Various technologies have been described in the art that involve promoting cell growth on the surface of biomedical implants. Examples of such technologies include (i) nanocoating of implant materials and (ii) porous scaffold based devices. However, these technologies are deficient in various aspects.
Nanocoating of Implant Materials:
This strategy utilizes the ability to nano fabricate a surface coating onto implanted devices which can act as the anchoring for cellular growth on the device surfaces. Made of bio-compatible materials, cell adhesion is promoted by surface structures and cell interaction with the coating. Electro-coating is often utilized to ensure a strong adhesion of the coating to the implantable device. The coating can be made from polypeptides or any material that may enhance cell adhesion and growth.
Porous Scaffold Based Devices:
The use of porous scaffolds has been developed to allow for cells or growth factors to be incorporated into implantable devices. This technique impregnates the device with pores that have a specific size depending on the desired applications. While this application allows molecules or cells to be incorporated into the structure, the entire device is a porous material, detracting from the integrity of the device.
Endothelial cells line blood contacting surfaces of the cardiovascular system, transducing hemodynamic signals and maintaining a non-thrombogenic surface. The drawback of many cardiovascular implants is the necessity for concurrent administration of anti-coagulant therapies. These implants require these drugs due to foreign surfaces contacting circulating blood components. Specifically, the blood-device interaction promotes platelet and clot aggregation on the device surface, rendering it a medical hazard. By thinning the blood with anticoagulants, patients are able to benefit from cardiac implants such as heart valves and stents without having to worry about clotting or platelet aggregation on their implanted cardiac devices. The drawback to taking blood-thinners is the altered capacity of blood. Patients taking blood thinners have a difficult time clotting when injured. Individuals needing cardiac implants are required to have a limited lifestyle upon treatment, dramatically reducing quality of life. This includes the inability to get pregnant, vast reduction in physical activity, and high risk of bleeding. Endothelial cells naturally regulate the blood clotting cascade (1). Coating the surfaces of these implanted devices with endothelial cells would prevent the need for anticoagulants as the passing blood would not be able to differentiate the endothelial coated implant from healthy vasculature. The biological coating of cardiac implants assists in maintaining a natural hemodynamic environment, one that is protected by endothelial cells, preventing or decreasing the need for anti-thrombotic drugs.
Clot formation occurs naturally by platelet aggregation, followed by clotting cascade initiation. Platelets are recruited to the injury sites via two separate pathways; the collagen and tissue factor pathways. The mechanism of collagen initiated platelet aggregation is dependent upon glycoprotein VI, and glycoprotein Ib (2). Endothelial secreted factors such as TFPI and PECAM-1 (3, 4).
Currently there are two types of aortic heart valve replacements available to patients in need of a new valve. One option is the biological valve, which is the implantation of another valve either from a different part of the heart, a cadaver or an animal; while the other option is a mechanical valve. Each of these options has a drawback; the biological valves degrade over time and need to be replaced, while patients that choose to have the mechanical valves need to take blood thinners as they are susceptible to blood clots. Further, patients on blood thinners face the significant potential for major hemorrhages because of the lack of clotting.
The present invention is directed to overcoming these and other deficiencies in the art.